In a camshaft free combustion engine a pressure fluid, such as a liquid or a gas, is used to achieve a displacement/opening of one or more engine valves. This means that the camshafts, and related equipment, that conventional combustion engines use to open engine valves to let air in respective let exhaust fumes out from the combustion chamber, has been replaced by a less volume demanding and more controllable system.
In an engine that is constructed for significant angular momentum outputs, the pressure in the combustion chamber is increasing proportional to an increased angular momentum output, and the force that is required to open the valve actuator to open the, in relation to the combustion chamber inward opening, engine valve is consequently also increases proportional to an increased angular momentum output. At high numbers of revolutions, such as 6-8000 rpm, a very fast opening of the engine valve is also required for the filling of air respective evacuation of exhaust fumes from the engine cylinder not to be restricted. These requirements, i.e. the need for an extremely fast opening at high frequencies in a high performance engine having high counter pressure in the combustion chamber of the engine at the opening of the exhaust valves, require the pressure of the pressure fluid upstream of the valve actuator to be high, in the order of 8-30 bar.
Downstream of the valve actuator, the pressure fluid has a lower pressure, in the order of 3-6 bar, and when the pressure of the pressure fluid shall be increased by way of a compressor from the low pressure downstream of the valve actuator to the high pressure upstream of the valve actuator, a temperature rise occurs that increases concurrently with an increased pressure condition.
It is desirable that the pressure of the pressure fluid that is led to the compressor is relatively low, and thereby more compact, for achieving a high efficiency of the compressor. Heat is added to the pressure fluid during the compression. If the pressure ratio between the high pressure side and the low pressure side is too high, it leads to a temperature of the pressure that is too high on the high pressure side, which increases the risk of oxidation of the oil that is used concurrently with increasing temperature of the pressure fluid. This means that a part of the increased temperature at the low pressure side has to be lowered by cooling, which leads to energy losses and a need for cooling equipment.
The pressure fluid circuit of the combustion engine is a closed circuit in which pressure fluid is conventionally led via conduits from a compressor to pressure fluid inlets of the valve actuators, and then led via conduits from the pressure fluid outlets of the valve actuators back to the compressor. During operation of the combustion engine, the need for pressure difference between the low pressure side and the high pressure side varies.
As a result of the pressure fluid circulating in a closed system, the compressor will at high pressure differences take air from the low pressure side and bring it over to the high pressure side. Hereby the pressure difference will increase, which is desirable. Unfortunately, the pressure ratio between high pressure side and the low pressure side will unfortunately increase, both due to the fact that the high pressure level rises and to the fact that the low pressure simultaneously falls. An increasing pressure ratio leads to the temperature of the pressure fluid increases downstream of the compressor.
Individual conduits from the outlets of the valve actuators additionally lead to pressure fluid limitations and increased complexity in manufacturing and assembling.